Coordinate Computation Device and Sewing Machine

1. A coordinate computation device comprising: a position indication portion that includes an indicating portion, a switch, and a transmitter, the indicating portion being configured to indicate a position on a plane, the transmitter being configured to transmit ultrasonic waves, and the position indication portion being long in a direction of a virtual straight line that passes through the indicating portion and the transmitter; a detection portion that is configured to detect the ultrasonic waves that are transmitted by the transmitter; a processor; and a memory that is configured to store computer-readable instructions, wherein the computer-readable instructions cause the processor to perform processes comprising: computing sets of first coordinates, based on times when the detection portion detects the ultrasonic waves, the sets of the first coordinates respectively indicating positions on the plane that respectively correspond to positions of the transmitter at a time when the switch is turned on and at times before and after the switch is turned on; computing a movement direction of the position indication portion on the plane, based on at least one part of the sets of the computed first coordinates; computing an angle that is formed between the plane and the direction in which the position indication portion is long, based on at least one part of the sets of the computed first coordinates; and computing a set of second coordinates, based on the computed movement direction, the computed angle, and a set of third coordinates among the sets of the computed first coordinates, the set of the second coordinates indicating an indicated point on the plane, the indicated point being the position that is indicated by the indicating portion, and the set of the third coordinates indicating a position on the plane that corresponds to the position of the transmitter at the time when the switch is turned on.

2. The coordinate computation device according to claim 1 , wherein the computing of the sets of the first coordinates includes computing a distance between the transmitter and the detection portion, based on a velocity at which the ultrasonic waves travel, times when the ultrasonic waves are transmitted by the transmitter, and the times when the detection portion detects the ultrasonic waves that are transmitted from the transmitter, and computing the positions on the plane that respectively correspond to the positions of the transmitter.

3. The coordinate computation device according to claim 2 , wherein the computing of the sets of the first coordinates includes computing, based on the times when the detection portion detects the ultrasonic waves, the positions on the plane that respectively correspond to the positions of the transmitter at times at each of which a specified time period elapses, starting from before the switch is turned on and continuing after the switch is turned on.

4. The coordinate computation device according to claim 1 , wherein the computing of the movement direction includes computing the movement direction based on a direction on the plane from a first point to a second point, the first point corresponding to one of the sets of first coordinates, the second point corresponding to another one of the sets of first coordinates, and coordinates of the second point indicating a position of the transmitter after the switch is turned on.

5. The coordinate computation device according to claim 1 , wherein the computing of the angle includes: computing a distribution density of the sets of the first coordinates on the plane in relation to the computed movement direction; and setting, with reference to a table, an angle corresponding to the computed distribution density, the angle and the distribution density being stored in association with each other in the table.

6. The coordinate computation device according to claim 1 , wherein the computing of the set of the second coordinates includes computing the set of the second coordinates based on a distance between the indicating portion and the transmitter.

7. The coordinate computation device according to claim 1 , wherein the position indication portion is an ultrasound pen.

8. A sewing machine comprising: a bed that includes a bed surface being a top surface thereof; a position indication portion that includes an indicating portion, a switch, and a transmitter, the indicating portion being configured to indicate a position on the bed surface, the transmitter being configured to transmit ultrasonic waves, and the position indication portion being long in a direction of a virtual straight line that passes through the indicating portion and the transmitter; a detection portion that is configured to detect the ultrasonic waves that are transmitted by the transmitter; a processor; and a memory that is configured to store computer-readable instructions, wherein the computer-readable instructions cause the processor to perform processes comprising: computing sets of first coordinates, based on times when the detection portion detects the ultrasonic waves, the sets of the first coordinates respectively indicating positions on the bed surface that respectively correspond to positions of the transmitter at a time when the switch is turned on and at times before and after the switch is turned on; computing a movement direction of the position indication portion on the bed surface, based on at least one part of the sets of the computed first coordinates; computing an angle that is formed between the bed surface and the direction in which the position indication portion is long, based on at least one part of the sets of the computed first coordinates; and computing a set of second coordinates, based on the computed movement direction, the computed angle, and a set of third coordinates among the sets of the computed first coordinates, the set of the second coordinates indicating an indicated point on the bed surface, the indicated point being the position that is indicated by the indicating portion, and the set of the third coordinates indicating a position on the bed surface that corresponds to the position of the transmitter at the time when the switch is turned on.

9. The sewing machine according to claim 8 , wherein the computing of the sets of the first coordinates includes computing a distance between the transmitter and the detection portion, based on a velocity at which the ultrasonic waves travel, times when the ultrasonic waves are transmitted by the transmitter, and the times when the detection portion detects the ultrasonic waves that are transmitted from the transmitter, and computing the positions on the bed surface that respectively correspond to the positions of the transmitter.

10. The sewing machine according to claim 9 , wherein the computing of the sets of the first coordinates includes computing, based on the times when the detection portion detects the ultrasonic waves, the positions on the bed surface that respectively correspond to the positions of the transmitter at times at each of which a specified time period elapses, starting from before the switch is turned on and continuing after the switch is turned on.

11. The sewing machine according to claim 8 , wherein the computing of the movement direction includes computing the movement direction based on a direction on the bed surface from a first point to a second point, the first point corresponding to one of the sets of first coordinates, the second point corresponding to another one of the sets of first coordinates, and coordinates of the second point indicating a position of the transmitter after the switch is turned on.

12. The sewing machine according to claim 8 , wherein the computing of the angle includes: computing a distribution density of the sets of the first coordinates on the bed surface in relation to the computed movement direction; and setting, with reference to a table, an angle corresponding to the computed distribution density, the angle and the distribution density being stored in association with each other in the table.

13. The sewing machine according to claim 8 , wherein the computing of the set of the second coordinates includes computing the set of the second coordinates based on a distance between the indicating portion and the transmitter.

14. The sewing machine according to claim 8 , wherein the position indication portion is an ultrasound pen.